perfcounters: fix refcounting bug, take 2

Only free child_counter if it has a parent; if it doesn't, then it
has a file pointing to it and we'll free it in perf_release.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
1 file changed